The DNA of a male harbored a deletion of exon 16 as well as most of introns 15 and 16 of the dystrophin gene. The person was completely healthy, with universal normal muscle strength, and normal muscle histology and creatine kinase levels. The deletion was also present in DNA from a muscle biopsy, excluding mosaicism as an explanation for the phenotype. We conclude that the protein segment encoded by exon 16 of the dystrophin gene is of no importance for the essential function of dystrophin. The findings suggest that even large gene re-arrangements of the dystrophin gene may not always be disease-causing, and caution a diagnosis of dystrophinopathy in sporadic cases of single exon in-frame deletions.
(c) 2006 Wiley-Liss, Inc.